Vacuum pumping arrangements used to pump fluid from semiconductor tools typically employ, as a backing pump, a multi-stage positive displacement pump employing inter-meshing rotors. The rotors may have the same type of profile in each stage or the profile may change from stage to stage.
Many semiconductor processes use or generate potentially flammable mixtures containing fuels such as hydrogen and silane. The pumping of such mixtures requires great care to be placed on the leak integrity of the foreline and exhaust lines from the pump to ensure that there is no ingress of air into the lines which could create a flammable atmosphere. Moreover, in some processes a fuel and an oxidant, for example TEOS (tetraethoxysilane) and ozone, may flow through the pump at the same time. In such circumstances any hot spots within the pump could provide intermittent ignition sources for the fuel, which could result in the generation of hazardous flame fronts travelling through the pump into the exhaust lines.
It is an aim of at least the preferred embodiments of the present invention to seek to solve these and other problems.